The present invention is directed to a device for cooling small hardware items and is located between a heat treating furnace and a quenching bath.
The requirements dealing with properties of heat treated parts are significant and increase continuously. The specified properties must be achieved as uniformly as possible in each individual part as well as within the entire charge of parts. Therefore, the heat treatment devices must fulfill the highest types of requirements.
Steel is heated to such a high temperature for heat treatment purposes that pearlite is transformed with certainty into austenite. The cubic body centered crystalline lattice of the ferrite changes over into the cubic plane centered crystalline lattice of the austenite. The resultant texture is designated as austenite. It is soft, tough as well as non-magnetic and forms grains with pointed corners.
Upon slow cooling, the texture is transformed back into its initial state.
To obtain a hardening or heat treatment of the part, cooling must occur very rapidly. The fine needle texture which is formed is very hard. It is called martensite.
A fluidized bed can be used as a quenching bath for hardening small hardware items, and in addition, a surface coating of the items can be effected. The hot items, such as small hardware items, for instance, bolts or nails, coming from the heat treatment station are directed to a fluidized bed where a fluidized powder is located. The heat content of the small hardware items entering the fluidized bed is determined by the thickness of the coating to be melted or fused onto the items.